We've talked in recent issues about the amount of time children are spending staring at screens – computers, tablets, laptops and mobile phones – and some of the health consequences, including poor posture. Physical activity also takes a hit in the face of excessive screen time, and children aren't the only ones at risk. Screen time and movement don't mix, regardless of age.

Case in point: a study that found Americans become more sedentary as they devote more free time to their screens, particularly their computers. Over a 15-year study period involving more than 50,000 people, ages and older, researchers discovered that average daily sitting time increased from seven to more than eight hours for teens, and from 5.5 to nearly 6.5 hours for adults. Coinciding with this increasingly sedentary behavior: an increase in average daily computer use (not at work or school).

By the end of the study period, nearly 60 percent of children / teens and 50 percent of adults were spending an hour or more of leisure time on a computer. While the study also found high percentages of children and adults who spent at least two hours daily sitting watching TV or videos (62 percent of 5- to 11-year-olds; 59 percent of 12- to 19-year-olds; 62 percent of adults ages 20 to 64; and 84 percent of older adults), these percentages appeared to remain stable during the study period.

Writing about their findings in the Journal of the American Medical Association, the researchers therefore suggest increased computer use, rather than increased TV / video viewing, is the likely reason why Americans of all ages are spending more time sitting and less time moving. Click here for suggestions on how to reduce your daily screen time, and here for simple ways to incorporate more physical activity into even your busiest day.